C63.27: Evaluation of RF Wireless Coexistence for Medical Devices- a new standard for R&D. DATE: Thursday, November 9th TIME: 2:30 pm-3:15 pm

Transcription

1 C63.27: Evaluation of RF Wireless Coexistence for Medical Devices- a new standard for R&D DATE: Thursday, November 9th TIME: 2:30 pm-3:15 pm

2 Agenda History of Wireless Medical Devices and the FDA concern Recent Events in Regulatory Standards What is RF Coexistence Testing? How is RF Coexistence Testing performed? Ensuring repeatability during medical device test

3 A look back to 2009

4 Sensor and RF Technology Driving Consumer Innovation Billions of IoT devices, many using the same radio bands Source: Posted in Research and Development [1] by MDDI Staff on May 8, 2017 Research and Development (

5 Medical Wearable trends Category Personal Health (Prevention) Clinical Research Disease Management Disease Diagnosis Therapeutics Description General fitness and wellness sensors having prevention-based UX Sensors for measuring biometrics and activity used in clinical research Sensors for chronic disease management such as COPD, asthma, diabetes, and cardiovascular disease Sensors for screening or diagnosing diseases such as sensors for atrial fib, arrhythmia, and hypoxia Sensors that provide active feedback for controlling therapeutic medical devices Example Products Omrom Wellness; HealthKit Actigraph products; BIOPAC products; ResearchKit Philips HealthSuite irhythm atrial fibrillation sensors; Omron hypertension screening Medtronic insulin pump systems and neurostimulators FDA Regulated No Typically not Yes Yes Yes very highly

6 FDA approval process often not the bottleneck Typical timeline of Medical Device development Device prototyping: 2 5 weeks Feasibility testing in the lab: 1 2 weeks Use case validation in the field: More than a year Independent clinical validation: More than 6 months FDA approval (510K): 3 9 months

7 Agenda History of Wireless Medical Devices and the FDA concern Recent Events in Regulatory Standards What is RF Coexistence Testing? How is RF Coexistence Testing performed? Ensuring repeatability during medical device test

8 Wireless Coexistence Today s Topic: Only one aspect of the FDA Wireless Guidance Selection and performance of wireless technology Wireless Coexistence Quality of Service EMC of the Wireless Technology Information for Proper Set-up and Operation Security of Wireless Signals and Data Considerations for Maintenance

9 The Need for Coexistence Testing The FDA work began in 2007 and issued first Guidance in 2013 If the RF wireless medical device is expected to be used in proximity to other RF wireless in-band (i.e., the same or nearby RF frequency) sources, FDA recommends addressing such risks through testing for coexistence of the device wireless system in the presence of the number and type of in-band sources expected to be in proximity to the device. Radio Frequency Wireless Technology in Medical Devices Guidance for Industry and FDA Staff, Section 3c, August 14,

10 Agenda History of Wireless Medical Devices and the FDA concern Recent Events in Regulatory Standards What is RF Coexistence Testing? How is RF Coexistence Testing performed? Ensuring repeatability during medical device test

11 Industry alignment: RF Coexistence AAMI TIR69:2017 Recommendations for the process and guidance on performing a radio-frequency (RF) wireless coexistence evaluation of a medical device as part of an overall medical device risk management approach. Refers to C63.27 as a foundation. Approved 28 February 2017 Includes sample reports and additional information to aid in FDA documentation C ANSI Standard for Evaluation of Wireless Coexistence Provides an evaluation process and supporting test methods to quantify the ability of a wireless device to coexist with other wireless services in its intended radio frequency (RF) environments. Published 11 May 2017 Major contributors to standards: H. Stephen Berger, Co-Chair Jason Coder, Co-Chair of NIST Nick LaSorte, Secretary of the FDA Key research contribution Hazem Refai, University of Oklahoma Tulsa.

12 What is Coexistence? It is not traditional EMI/EMC testing EMC Testing: EMI tests emission of unintended RF signals EMC tests susceptibility to signals other than the intended frequency Coexistence Testing: Evaluates the ability of a device to maintain its functional wireless performance (FWP) Tests both intended and unintended (interfering) signal impact on the device Both co-channel and nearby frequencies Different radio modulation formats (concern: WiFi and Bluetooth both at 2.4 GHz)

13 Background History: Coexistence Factors Factors determining coexistence: Logical Layer and the Physical Layer Standard Frequency Data Rate Range Inductive Coupling < 1 MHz 1-30 kbps <1m Wireless Medical Telemetry System MHz >250 kbps 30-60m MHz, MHz Medical Device Radiocommunication Service MHz 250 kbps 2-10m Medical Micropower Networks ( MMNs ) , , , MHz <1m Medical Body Area Networks ( MBANs ) MHz 10Kbps-1Mbps <1m a Wi-Fi 5 GHz 54 Mbps 120m b Wi-Fi 2.4 GHz 11 Mbps 140m g Wi-Fi 2.4GHz 54Mbps 140m n Wi-Fi 2.4/5GHz 248 Mbps 250m Bluetooth Class I 2.4 GHz 3 Mbps 100m Bluetooth Class II 2.4 GHz 3 Mbps 10m (Zigbee) 868, 915 MHz, 2.4 GHz 40 kbps, 250 kbps 75m World Interoperability for Microwave Access (WiMAX) 2.5 GHz 70 Mbps (fixed), 40 Mbps (mobile) Several km Considerations when selecting the Medical Device wireless modality. Risk based evaluation Testing to mitigate the risk to acceptable levels Common Short and Long Range Wireless Devices for Patient Monitoring, Control and Diagnostics

14 1 Coexistence Factors at the Physical Layer Dependent on three factors: 1. Frequency: The probability of coexistence increases as the frequency separation of channels increases between wireless networks. 2. Space (range): The probability of coexistence increases as the signal-to-interference-ratio of the intended received signal increases due to physical separation. 3. Time: The probability of coexistence increases as the channel occupancy of the wireless channel decreases. Coexistence is possible given one of the three following conditions: Adequate frequency separation between wireless networks. Sufficient distance between wireless networks, effectively decreasing the signalto-interference ratio (SIR) in each. Relatively low overall occupancy of the wireless channel.

15 1 Problem #1: Frequency Many devices trying to use the 2.4 GHz ISM Band Non-Overlapping Channels (2.4 GHz): a/g/n.. (WiFi) (ZigBee) (Bluetooth) Bandwidth 22 MHz 5 MHz 1 MHz One way to increase the coexistence of heterogeneous networks is to employ adaptive frequency hopping. The Bluetooth transmitter and/or the receiver senses the channels to establish which of the 79 Bluetooth channels are free and busy. Bluetooth infers which channels are free and busy by observing the packet error rate of each channel. If a channel has a high packet error rate, it is identified as busy.

16 1 Problem #2: Space What is the physical relationship between intended and interfering devices? WiFi Hotspot Phone WiFi AP1 ZigBee 1 ZigBee 2 WiFi AP2 WiFi Client Device WiFi AP3

17 1 Problem #3: Time What signals are on the air at the same time? WiFi WiFi BT WiFi BT! ZigBee ZigBee! WiFi Time b/g contains abundant white space % white space with maximum data rate The existing coexistence mechanism for ZigBee, such as carrier-sensing multiple access (CSMA), are inadequate to utilize the white space. The default clear channel assessment (CCA) for b/g is that it only tries to sense other b/g signals b/g does not defer their transmission even when there are existing ZigBee transmissions.

18 Coexistence Factors: Logical Domain vs Physical Domain Wireless Techniques Push Analysis to Higher Layers OSI Layer Application Presentation Session Transport Example Human Interface Compression Permissions TCP (end-to-end) Logical Domain In a wireless network, typical functions in the Logical Domain include Routing, System Capacity, Battery Life, Reliability Margin, Spectrum Utilization, End-to-End Error Correction, Session Connectivity Network Data Link Physical IP (addressing) Error Detection, Flow Control RF Modulation, Frequency Physical In a wireless network, functions in the Physical domain include Frequency, Modulation Type, Bit Rate Interference Analysis now covers more than PHY

19 Agenda History of Wireless Medical Devices and the FDA concern Recent Events in Regulatory Standards What is RF Coexistence Testing? How is RF Coexistence testing performed? Ensuring repeatability during medical device test

20 How Does ANSI C63.27 Define the Process? ANSI C63.27 Wireless Coexistence Evaluation Process Clause 5 Test Plan Development Clause 6 - Testing Clause 7 Analysis & Summary of Test Results Clause 7 provides guidance for the most popular test objectives Clause 8 Analysis of Uncertainties

21 Four General Coexistence Test Methods 1. Conducted (Wired) (EUT = Equipment Under Test) Performed by combining the intended and unintended signals and connecting them to an access port next to or in place of the antenna Effects of the antenna are excluded from testing Possible to account for MIMO, beamforming, but difficult Most repeatable but least realistic test method Spectrum Monitor

22 Four General Coexistence Test Methods 2. Chamber/Hybrid Method Spectrum Monitor The signals are generated by actual equipment, which is placed in a separate chamber to allow control over the signal to which the EUT is exposed Channel effects can be accounted for. Effects of the antennas are included in the testing Also used in NFPA radio testing[1] [1] K. A. Remley and W. F. Young, "Test methods for RF-based electronic safety equipment: Part 2 Development of laboratory-based tests," in IEEE Electromagnetic Compatibility Magazine, vol. 2, no. 1, pp , 1St Quarter doi: /MEMC

23 Four General Coexistence Test Methods 3. Radiated-anechoic method Semi or fully anechoic chamber Ensures that the environment does not decrease the repeatability of the test results Antenna effects are accounted for. Environment may not resemble the deployment environment Spectrum Monitor

24 Four General Coexistence Test Methods 4. Radiated Open Lab Method No shielded room Designed to be able to test any wireless device(s) Devices can be in LOS or NLOS configuration Enables replication of the deployment environment. Testing can be susceptible to ambient signals Spectrum Monitor

25 Interferer types, recommended equipment for testing See Annex A of C63.27 for Band-specific test guidance To test Bluetooth and BLE: Tier 3: single test: Single n signal 64 QAM Tier 2: two tests: Two n signals 64 QAM Two adjacent-band LTE signals Tier 1: two tests: Three n 64 QAM Two adjacent-band LTE signals To test WiFi at 2.4 GHz: Tier 3: single test: Single n signal 64 QAM Tier 2: three tests: One co-channel n One adjacent-band lower LTE signal One adjacent-band upper LTE signal Tier 1: three tests: Two concurrent n lower/higher CH One adjacent-band lower LTE signal One adjacent band upper LTE

26 Evaluation Tiers Based upon Risk Levels (Probability, Severity, etc ) EUT Using Bluetooth: Test Tier Unintended Signal Instruments Tier 1: Lowest Risk a single IEEE n transmission N5182B MXG Vector Signal Generator or M9381A PXI Vector Sig Gen Tier 2: Medium Risk Test A: Two n transmission Test B: Two Adjacent-band LTE signals N5182B MXG Vector Signal Generator or M9381A PXI Vector Sig Gen Tier 3: Highest Risk Test A: Three n transmissions Test B: Two Adjacent-band LTE signals N5182B MXG Vector Signal Generator or M9381A PXI Vector Sig Gen Spectrum Monitor n/a N9020B MXA, or N9914 Field Fox with RTSA

27 Evaluation Tiers Based upon Risk Levels (Probability, Severity, etc ) EUT Using 2.4 GHz WiFi: Test Tier Unintended Signal Instruments Tier 1: Lowest Risk a single IEEE n transmission N5182B MXG Vector Signal Generator or M9381A PXI Vector Sig Gen Tier 2: Medium Risk Test A: One n transmission Test B: One adjacent-band LTE signal U Test C: One adjacent-band LTE signal L N5182B MXG Vector Signal Generator or M9381A PXI Vector Sig Gen Tier 3: Highest Risk Test A: Two concurrent n transmissions U and L channels Test B: One adjacent-band LTE signal U Test C: One adjacent Band LTE signal L N5182B MXG Vector Signal Generator or M9381A PXI Vector Sig Gen Spectrum Monitor n/a N9020B MXA, or N9914 Field Fox with RTSA

28 Agenda History of Wireless Medical Devices and the FDA concern Recent Events in Regulatory Standards What is RF Coexistence Testing? How is RF Coexistence testing performed? Ensuring repeatability during medical device test

29 Design Controls Design History File Documented repository of everything that happened in the design process. The Device Master Record Each time the DMR is updated, it is placed in the DHF along with the Validation process that was used to approve the changes. Provides evidence that you have designed according to design controls. 21 CFR

30 Ensuring Repeatability During Medical Device Test 1. Use off the shelf instrumentation traceable to NIST standards 2. Be able to trace software controlled measurement test steps 3. Use dedicated product fixturing to: a. Reproduce the verification steps after a revision change (CAPA or audit). b. Ensure quality in production

31 Ensuring Repeatability During Medical Device Test 2. Automate your Test Software Requirements Management Implementation Software Requirements Unit Tests Test Results

32 Ensuring Repeatability During Medical Device Test 3. Create or purchase fixed function product Fixturing for test repeatability.

33 Example RF-based Design Verification Test Fixture for DVT

34 Ensuring Repeatability During Medical Device Test How best to align with QMS and GAMP standards in Production Organize the test system resources for maintainability Limit use of custom cables if possible Limit the number of touch-points made by test operator for cable connections before test Limit the number of test stage transitions and handling by the operator

35 Ensuring Repeatability During Medical Device Test A. Organize the test system resources for maintainability

36 Ensuring Repeatability During Medical Device Test B. Minimize hand made custom cabling PCB or hard-wired interface between PXI modules and receiver

37 Ensuring Repeatability During Medical Device Test C. Limit test stage transitions and operator handling Multi-modality tester with a common ATE base and interchangeable fixtures.. Modular nest for product variants. CCI 1050 Medical Device Test Station Integrated through-connector and RF test